Stationary gyroscopic compass



4 Sheets-Sheet l FIC-il Filed March 23, 1960 /NVE/VTRS Jzo hannes Hinze Hams ErL'c/l amt Argara] Dec. 29, 1964 J. HlNTzE ETAL STATIONARY GYRoscoPIc COMPASS Filed March 23, 1960 4 Sheets-Sheet 2 anni Ham; Ehrz'ch Dec. 29, 1964 |.H1NTzE ETAL 3,162,951

STATI-0mm GYRoscoPIc coMPAss Filed March 23 1960 4 Sheets-Sheet 3 INVENTORS ha/mas Hl'n tze and. Han. E'mzh DeC. 29, 1964 J, HlNTzE ETAL 3,162,951

STATIONARY GYROSCOPIC COMPASS Filed March 25 1960 4 Sheets-Sheet 4 //V VENTRS hannes Hin tze and [[405 ECA United States Patent O Mice 3,162,951 STATIONARY GYRSCOFIC COMPASS .lohannes Hintze, Kiel, and Hans Enrich, Kiel-Schulensee,

Germany, assignors to Anschutz 2r Co., Gandini-1., Kiel- Wik, Germany, a German company Filed Mar. 23, 1960, Ser. No. 17,094 Claims priority, application Germany, Mar. 31, 1959, A 31,716 11 Claims. (Cl. 315-72) Our invention relates to a stationary gyroscopic compass serving the purpose of turning a theodolite into registry with the meridian for geodetic purposes.

It is the object of our invention to provide an improved gyroscopic compass of this kind which aligns the theodolite with the meridian with great accuracy and constancy of any possible deviation and which, after having been put in operation at any particular location, will come to rest within a minimum of time of the order of ten minutes or less. Y

Further objects of our invention are to provide a compass of the kind described which is of rugged structure and not liable to be vdamaged in transportation from one place to another and requires a minimum of maintenance but is reliable and accurate in operation and of compact design and has a long life.

Finally, it is an object of our invention to provide an improved stationary gyroscopic compass equipped with control means for stopping the electric motor preparatory to transport of the compass to another location.

Further objects of our invention will appear from a detailed description of a preferred embodiment of our invention following hereinafter with reference to the accompanying drawings. It is to be understood, however, that our invention is not limited to such details but is capable of numerous modifications within the scope of the appended claims and that the terms and phrases used in such detailed description have been chosen for the purpose of explaining rather than that of restricting or limiting our invention.

In the accompanying drawings in which a preferred embodiment of our invention is illustrated FIG. 1 is a vertical longitudinal section of our stationary gyroscopic compass, the float thereof being shown in elevation,

FIG. 2 is a sectional View of the lower part of the housing similar to FIG. 1 but on an enlarged scale,

FIG. 3 is an electrical circuit diagram including an isometric view of the electrodes shown in FIG. 1, and

FIG. 4 is an electrical circuit diagram illustrating control means for stopping rotation of the gyroscope.

A tripod, preferably of the type having extensible legs of the telescope type, is provided with an annular top 11 provided with three circumferentially distributed threaded bores, each bore accommodating an adjusting screw 12 projecting above the top face of the annular member 11 to engage a downwardly facing shoulder 13 of a container which comprises an upper cylindrical portion 14 of larger diameter, a lower cylindrical portion 15 of smaller diameter with the shoulder 13 atthe juncture of portions 14 and 15, a top cover 16 and a bottom cover A 17. By means of the adjusting screws 12, the container can be easily so adjusted that its vertical axis 18 extends exactly in vertical direction. For the purpose of facilitating such adjustment, the compass is providedwith a level 19.

The container is filled with a liquid 2l) and encloses a iloat 21 therein. Preferably, the liquid is electrically conductive and may be formed by acidlied water.

The container 14, 15, 16 and 17 and the float 21 have a shape affording them freedom for relative rotation about the Vertical axis 18. In the embodiment illustrated, both 3,162,951 Patented Dec. 29, 1964i the internal walls of the housing sections 14 and 15 and the external walls of the float 21 are surfaces of revolution coaxially disposed with respect to the axis 18.

The float comprises an upper substantially cylindrical housing 22 and a weight mounted on the bottom of housing 22 and comprising a stem 23 extending downwardly from the bottom of the housing 22 and a head 24 fixed to the stem 23 and extending into close vicinity of the bottom cover 17.

A gyroscope diagrammatically indicated at 25 is carried by the float 21 with its axis of rotation in horizontal position. More particularly, standards 26 and 27 are mounted on the bottom of housing 21 and carry coaxial bearings having a horizontal axis and mounting the shaft of the rotor of the gyroscope, the rotor including an electric motor 28 (FIGS. 3 and 4) of the three-phase type. As gyroscopes of this kind are well known in the art, a detailed description thereof is deemed dispensable herewith.

The iloat 21 and all of the elements carried thereby including the gyroscope 25 are so designed that its center of gravity is located a substantial distance below the center of buoyancy of the lloat 21. The weight 24 serves to increase such distance.

A theodolite 28 is mounted on the container 14, 15, 16 and 17 for rotation about the Vertical axis 18. More particularly, the top cover 16 is formed with a sleeve 29 disposed coaxially to the axis 18 and surrounding a pair of antifriction bearings 30 and 31 in which a hollow shaft 32 is journaled. The hollow shaft 32 has an upper horizontal flange 33 which is embraced by and fixed to the cylindrical depending flange 34 of a circular table 35. The theodolite 2-8 rests on and is fixed to the table 35. The elements 32, 33, 34, 35 and 28 are thus mounted for common rotation, although they may be relatively rotatably adjustable about the axis 18, if desired.

Suitable means are mounted on one or both of the elements formed by the container and the float 21 for exerting a force on the lloat 21 to maintain same in floating condition. Such means are well known in the art. They may comprise a coil mountedon the head 24 in coaxial relationship to the axis 18 and energized by alternating current for the purpose of inducing eddy currents in the bottom cover 17 made of a conductive material, such eddy currents exerting a repelling force upon the coil, thus keeping the same spaced from the cover 17. As the provision of such a coil is well known in gyroscopic compasses (see British Patent 682,908, coil 20), an illustration thereof is deemed dispensable herewith. Preferably, however, the means exerting a force on said float maintaining it in floating condition is formed by a flexible traction member, such as a metal strip 36 having its upper end mounted in fixed relationship to the theodolite 28 and having its lower end fixed to the float 21 and extending along the Vertical axis 18. The weight of the float 21 and the elements carried thereby exceeds the buoyancy of the float and, therefore, Will keep the metal strip 36 taut. More particularly, the strip 36 extends from the center of the top of the lloat 21 through the hollow shaft 32 and its upper end is fixed to a circular member 37 which is rotatably supported by an antifriction bearing and is adjustably fixed to the flange 33.

A follow-up motor 38 is provided for producing relative rotation of the container and the theodolite about the vertical axis 18. In the embodiment shown, electric motor 3S is a reversible two-phase alternating current motor mounted on the top cover 16 of the container. lts" shaft is geared to a lay shaft 39 by a pair of meshing spur gears and a bevel pinion 4G fixed to the lay shaft 39 meshes with a bevel gear 41 fixed to the flange 34. Hence, rotation of motor 38 will cause rotation of the theodolite 2S relative to the container i4, l5, l5 and l? about the axis 18. l

Sensing means are provided `for sensing the relative angular position ofl the theodolite 23 and theiloatV Zi. In the embodiment shown, this sensing means comprises a flange 42 and four circumferentially distributed electrodes 43, 44, i5 and 46 carried thereby in closely spaced relationship tothe upper peripheral cylindrical surface 47 of the housing 22. The ange 42 is xed to the lower end of shaft 32 which extends downwardly through a central opening of the top cover 16 into the interior space of the container filled by the liquid. The electrodes 43-.46 cooperate in a manner to be described later with a pairof electrodes 4S and 49 provided on the cylindrical surface 47. Suitable control means to be described hereinafter are connected to the electrodes i3-i6 and to the reversible conical-depressions 55 and o7 will lock the float El within the container in coaxial relationship to the axis l thereof. Preferably, suitable indicating means are associated I with the manually operablemeans 55 for indicating the follow-up motor 3S for causing the latter to impart ollowup rotation to the theodolite 2S relative to@ the oat 2l.

Suitable dampingmeans are provided to dampen rotary oscillations about the vertical axis 156. As such damping means are well known in the art, Va detailed description thereof is deemed dispensable herewith. Vln FIG. l such damping means Vare illustrated as aneddy current brake f comprising a perinanenthorse-shoe magnet di? so mount- A thermostat-controlled annular heating element 5% is disposed within the liquid surrounding the head 24 and serves the purpose of maintaining the temperature of the liquid as constant as possible.

As it is desirable to lock the iioat '2l in iixed relation-l ship to the container 14, 15, i6 and l? during transportation in order Vto preclude erratic movements of the float liable to damage it, we have provided arresting means mounted on the container for engagement with the lioat causing same to be locked in coaxial relationship to the container, and manually operable means for op-V tionally rendering said arrestingrmeans effective and ineiective. lin the embodiment shown, the arresting means comprises a plunger Si having a depending coargial hollow stern 52 slidably guided within a central vertical bore of aV bracket 55 which is fixed to Vthe bottom cover 17 and has a horizontal bore accommodating a Vshaft S4 of a knob 55. An eccentric pin'StS proiecting from the inner end of stem 54 extends through a lateral aperture 57 of the hollow stern 52 vbelow a piston 5S which isv slidbearings 3d and 3l have to carry a very slight thrust l ctective condition and the ineffective condition of the arresting means 5l. in the Vembodiment shown such indicating means are formed by'a coat 6% of red paint cover-V ing half of the knob and facing upwardly, when the parts assume the position illustrated in FlG. 2 in Vwhich the iioat is in lioating condition and, therefore, isV in Vtoo sensitive a condition to withstand transportation.

The operationof our improved gyroscopic'coinpass'is as follows: After the tripod 10,13 has been erected and the container 7.11:, l5, '16, and'z'/ has been inserted therein, the adjusting screws i2 are so adjusted as to'bring airis 1d in` accurately vertical position. Then the knob 53 is so turned that its red coat e3 faces upwardly. Thereafter, the gyroscopic compass is electrically hooked up to a motor-generator 7l causing the gyroscope to spin, PEG. 4. As a result, the rotation of earth will cause the gyroscope 25 to swing its airis of rotation about the axis i8 towards the meridian, thus producing an oscillation of the iloat 2l about airis: i3, such oscillation being damped bythe damping means o9 and Titi. After about ten minutes, the iioat'zl will have come to rest. During these oscillations the electrodes i3-i6 and the elements 2S, 32, 33a, 34, 35 and 4.2 connected therewith for common rotation are so driven by the follow-up motor 38 as to maintain the theodolite Lid in an invariable angular positionV relative to the oat 2l. Therefore, after theV float 21 will have come to rest, the theodolite will be in accurate alignment with the` meridian having been so adjusted fully automatically. l

The weight of the iloat will exceedthe buoyancy thereof by a very small force only. As a result, the antifriction only and will, there/fore, otter no substantial frictional resistance to the'ollow-up motor 3S. Owing to t. e largeV distance of the center of gravity oi the iioat from its center of buoyancy, 'the period or" oscillation of the oat about asis i8 under the edect ot the Vrotation oi the l'earth will'be very :short amounting to a few minutes The disposition of the 'gyroscope 2S in the upper portion 22 of theV float El o'lers the advantage that the heat roducedrby the electric drivingrnotor oi the gyroably guided within the stern 52. A helical pressure spring A 59 is inserted in the yhollow stem 52 between the piston 5S and the plunger Si. A diaphragm d@ clamped to the bottom shoulder ofthe plunger 5l by an annular nut 6l has its peripheral marginal portion tightly clamped between the bracket 53 and a cylindrical ilange 52 of the bottom cover i?. The latter is provided with a central opening 63, through which plunger 5l projects into close vicinity of the `head 24 of vthe float 21. Preferab y, Va

central conical projection 64 is provided on the bottom face of the head V21% in opposed relationship to a conical Y depression provided on the top face of the plunger 5l.

` The top face of the housing 22 is provided with a conical projection 66 in opposed relationship to butV normally spaced from a conical depression 67 provided in the bottorn of llange 42 coaXially to axis 13.

. For the purpose of transporting the gyroscopic compass,

the knob SS is turned from the position shown in FIG.' 2 by causing the eccentric pin S6 to lift the piston 58 and to bias spring S9 which will raise plungerV Si. into contact with the iloat 2l raising the latter andV causing the projection 66 to engage the depression 67;, As a result,

, engagement of the conical proiections and de with the scope Vand transferred to the liquid 2@ will produce a minimum of convection currents only because of the relatively short distance between the source o' heat and the top voi the container..

it is desirable that the gyroscopic compass will beready Y for transportation right afterthe geodetic measurements to be carried out with the theodolite 2d will have been completed. it is necessary, however, to postpone transportation until the gyroscope will have stopped its rotation control means vfor reversing the torque produced by the driving motor 23' ofthe gyroscope. Reversal ofV this torque results ina quick stoppage of the gyroscope whi'clnj in the absence of such control means, would continue to run with high speed for a considerable period ottime because of the small magnitude of the friction in relationV to the momen-tum of the gyroscope. The control means for reversing the `torque of motor 2S are illustrated in PEG. 4.' The input terminals '72v and 73 of the rnotor generator 7i. may beconnected to theterminals dtand .75 of a source of direct current through the intermediary of normally open contactsv 7d and 7? coand 3.

erator 71 supply a three-phase alternating current to the electric motor 2S of the gyroscope through the intermediary of normally closed contacts 82, 83 and 84 respectively, cooperating with armatures or a relay whose winding 85 is included in a circuit comprising terminal 75 of the source of direct current, lead 86, winding 85, lead 87, normally open contact 88 of relay 7 8, conductor 89, right-hand contact of switch 79, lead 90 and terminal 74. In FIG. 4 this circuit is shown in a condition in which it is interrupted by switch 79. Therefore, the normally closed contacts 82, 83 and 84 connect the electric motor 28 to the terminals 80, 81 and 82 for forward rotation.

For the purpose of stopping the rotation of the gyroscope, switch 79 is shifted to its right-hand position. This does not cause deenergization of the winding of relay 78 because the latter remains included in a circuit comprising terminal 75 of the source of direct current, lead 91, winding of relay 7 8, lead 92, normally closed Contact 93 of a relay 94, lead 95, normally open contact 26 (now closed) of relay 78, lead 97, lead 00 and terminal 74. Therefore, contacts 76, 77, 88 and 96 remain closed, until the holding circuit will be opened by energization of relay 94. The winding of relay 85, however, will be energized owing to the shifting of switch 79 to its righthand position. Therefore, the terminals 80, 81 and 32 will be connected with the normally open contacts 98, 99 and 100 of relay 85. Whereas terminal 102 of motor 28 will remain connected with terminal 80, the connection of terminal 103 will be shifted from terminal 81 to terminal 82 and the connection of terminal 101 will be shifted from terminal 82 to terminal 81 of the motor generator. As a result, the torque produced by the electric motor 28 will be reversed. A time switch is provided which will energize relay 94 to disconnect the motor generator 71 from the source of direct current 74, 75 after a certain period of time has elapsed since the energization of relay 85. In the embodiment shown, a transformer 104 has its input terminals connected to terminals 101 and 103 and has its output connected in circuit with a rectier 105, a normally open Contact 105 of relay 85, an adjustable resistor 107 and a capacitor 108. Energization of relay 85 Will close the normally open contact 106, thus causing the capacitor 108 to be charged through the resistor 107 causing the voltage across its terminals 109 and 110 to be gradually raised at a slow speed. As soon as this voltage has been raised to a level suiiicient to render a gas-illed tube 111 conductive, relay 94 placed in circuit with terminals 109 and 110 and tube 111 will be energized, thereby opening contact 93, thus interrupting the holding circuit for relay 78 which will be deenergized and will open its contacts 96, 76, 77 and 88, thereby disconnecting the motor generator 71 from the source of current 74, 75. This happens when the braking torque produced by motor 28 will have slowed down the gyroscope 25 substantially to stoppage. Deenergization of relay 78 causes the contact 88 to be opened, thereby deenergizing relay S5. As a result, contact 112 will be closed, thus shortcircuiting and discharging the capacitor 108.

In PIG. 3 we have shown a circuit diagram showing the means for supplying the electric current through the liquid to the electric motor 28 and the control means connected to the sensing means 435-49 and to the oilow-up motor 38 for causing the latter to impart follow-up rotation to the theodolite 28 relative to the float 21.

The internal surface of the container 14, 15, 1d and 17 and the external surfaces of the lower end of the hollow shaft 32, of the flange 42 and of the iloat 21 are coated with an electrical insulating material. This coat, however, does not cover the electrodes 43 to 46, 48 and 49 described hereinabove. While we have illustrated terminals 101, 102 and 103 in FlG. 4 as being directly connected to the contacts of relay 85, such connections include pairs of electrodes shown in FIGS. 1 One pair of electrodes comprises a ilat annular conductve strip 115 mounted on the inner face of the bottom cover 17 coaxially to axis 18 and an opposed ati annular strip 116 mounted on the bottom face of head 24, both strips 115 and 116 being mounted in VContact with the liquid 20. The strip 116 is connected by a conductor 117 to motor terminal 103, whereas the strip 115 is connected by a conductor 118 to contacts S3 and 98 of relay 85 as shown in FIG. 4. A second pair of electrodes comprises a flat annular strip 119 iixed to the bottom of container 22 and an opposed fiat annular .strip 120 xed to the internal shoulder provided between the container sections 14 and 15. Strip 120 is connected by a lead 121 to terminals 82 and 99 of relay 85, whereas strip 119 is connected by a lead 122 to terminal 101 of motor 28. The third pair of opposed electrodes cornprises a cylindrical conductive strip 123 xed to the interior peripheral face of portion 14 of the container between the ends thereof and a cylindrical conductive strip 124 xed in opposed relationship to the strip 123 to the external peripheral face of the housing 22. The strip 124 is connected by a lead 125 to terminal 102 of the electric motor 28, While the strip 123 is connected by a lead 126 to the terminals 84 and 100 of the relay 85. 1t will be noted from'FIG. 1 that the three pairs of annular strips are spaced a considerable axial distance from each other owingto the great axial length of the oat. As a result, the currents ilowing axially between the strips 115, 120 and 123 are reduced to a minimum as is desirable in order to reduce the heating effect of the current on the liquid as much as possible.

The follow-up motor 38 is a reversible two-phase alternating current motor having a phase winding 127 permanently connected between terminal 81 of the motor generator set 72 and a lterminal 128 thereof which is grounded. Therefore, phase Winding 127 will be energized with alternating current of an invariable phase. The other phase winding 129 of the follow-up motor 38, however, is energized with an alternating current of the same frequency of preferably 333 cycles per second which may be shifted through 180 so as to either lag behind the phase of the current through winding 127 or to precede it. For that purpose, the winding 129 is connected to the output of an amplifier 130 whose input constitutes the diagonal of a bridge circuit connected between motor terminal 102 and zero terminal 128. One branch of this bridge circuit comprises a lead 131, a resistor 132, a lead 133, the electrodes 44, 46, a conductive path constituted by the liquid 20, electrodes 48 and 49 and leads 134 and 135. The other branch of the bridge circuit comprises a resistor 136, a lead 137, the electrodes 43 and 45, a conductive path constituted by the liquid 20, the electrodes 48 and 49, the leads 134 and 135 and the terminal 102. The input of the amplifier 130 is connected to the leads 133 and 137. The follow-up motor 38 has the tendency of maintaining the theodolite in such an angular relationship to the lloat 21 that the electrode 48 is equally spaced from the electrodes 43 f and 44 and that the electrode 49 is equally spaced from the electrodes 45 and 46'. As a result, equal resistances are put in series with the leads 133 and 137 causing equal potentials to be applied to 'the input terminals of the amplifier 130. As a result, the output voltage of the ampliiier 30 is zero and the follow-up motor rests. Rotation of the lloat relative to the theodolite 28 mounted for common rotation with the electrodes 43-46 in clockwise direction reduces the resistance in series with conductor 133 and, at the same time, increases the resistance in series with the conductor 137. As a result, a voltage is produced at the output terminals of the amplifier 130 causing the follow-up motor to rotate in such a direction as to turn the theodolite and the electrodes 43 to 46 connected therewith likewise in clockwise direction until the output voltage of amplier 130 disappears. A voltage of the opposite polarity, however, will be produced at the output of the amplifier 130, when the lloat Z1 turns 1 Y in anticlockwise direction with reference to the theodolite. AsV aresult, the followup motor will keep the set of electrodesAS-to very accurately within the reiativerposition to thefloat 21 which is illustrated in Fi-G. 3.

A feature of particular importance is the interposition of the pressure spring S9 between the arresting rneans'iV trodes 43-46to a minimum in order to reduce a relative angular displacement thereof about axis 1S owing Vto torsional strains of the container 22. While the sensing means for sensing the angular position of the theodolite relative to the float with'respect tothe vertical axis i8 are formed by electrodes functioning in an electrolytic manner, any other sensing means will known in the art may be substituted, such as inductive sensing means or capacitively operating sensing means.V

Also the damping means 69, '79 may bereplaced by any other means capable of'dampening the oscillations of the iioat 21 about the axis i8.

FromV the foregoing it will be seen that this invention is onewell adapted to attain all of the ends and objects hereinabove yset forth, together with `other advantages which are obvious and which are inherent to the apparatos.

While the invention has been described in connection With a preferred embodiment thereof, it will be understood that it is capable of further modification, and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the

' principles ofthe invention and including suchdepartures from the present disclosure as come within known or customary practice in the art to which the invention pertains, andas fall within the scope of the invention and the limits of the vappended claims.

What we claim is:y v

l. Stationary gyroscopic compass comprising a con- `tainer, a liquid filling said container, a oat in said liquid,

roe-ans mounted on at least one of the elements formed by said container and said float for exerting a force on said lioat maintaining the floating condition thereof, a gyroscope carried by said iioatwith its axis of rotation in horizontal position, said'container and said oat having a shapefaifording freedom yfor relative rotation about a verical axisfand the center of gravity of said float and the elements carried thereby including saidA gyroscope being located a substantial distance below the center of buoyj ancy ofsaid lioat, a tlieodolite mounted on said container v for rotation about said vertical axis, sensing means connected with saidl theodolite orsensing the'angular position ofsaid theodolite relative to' said ioat with respect to said vertical axis, said iirst-named means including a iiexible elongated vertical suspension,memberV disposed above said float and having its lower end iixed to said iioat and its upper end to said theodolite, a follow-up motor connected with said container and to said theodolite for producing relative rotation thereof about said vertical axis, .control means connected to said sensing means and' to said motor for causing the latter to impart follow-up rotation to Asaid theodolite relative to said float keeping said suspension member in relaxed condition, and dampingmeans on said lioat to dampen rotary oscillationsV thereof about said vertical axis, the spin of said gyroscope being so correlated to the weight of said float and of annessi amplitude of said oscillations to substantially zero within'a period'of the order of ten minutes.

2. The combination claimed'in claimil in which said i float is formed by a housing, said combination further comprising means within said housing for mounting said gyroscope for rotation Yabout a-horizontal-V axisV and a weight mounted on thebottom of said housing, f

3. The combination claimedV in claimV 2 in which said weight extends downwardly from the bottom of said housing.

4. The combination claimed in claim l in which saidV theodolite is disposed above 'said float, and said means mounted on said container for exerting a force on said float is formed by a liexible traction member having its upper end mounted in xed relationship to said the'odolite and having its lower end fixed to said float `and extending along said vertical axis, the Weight of said float exceeding the buoyancy thereof.

5. The combination claimed in claim l in which said sensing means includes at least one electrode lixed to said Y tioat in contact with said liquid and at least one other electrode mounted in iixed relationship to saidk theodolitein Contact with said liquid in opposed relationship to said inst-mentioned electrode, and a source of alternating current connected to said electrodes.

6. The combination claimed` in claim 1 further comprising an electric motor connected to said gyroscope for driving same, pairs of opposed electrodes each pair corn-V prising one electrode mountedron said iioat in' contact with saidliquid and Vanother electrode mounted on said container in contact with said liquid, a source or current, and circuit means including said pairs of opposed electrodes and connected to said source of current and to Vsaid* electric motor for supplying electric power thereto.

7. The combination claimed in claim l further comprising an electric motor connected with said gyroscope for producing a torque driving the latter, a'source of current, circuit means connecting said source of current with said electric motor` for supplying electric power thereto,

Vengagement with the oat causing same'to be locked in the elements carried thereby, to said buoyancy, to said' distance and to the damping force exerted by said damping means as to resultV in a period of said oscillations amounting to a few minutes and in a reduction of the coaxial relationship toV said container, and manually operable means for optionally rendering said arrestingmeans eiiective Vand inedective. l l0. The combination claimed'inV claim 9 further comprising indicating means associated with said manually operable means forindicating the eective condition an the inefiective condition of said arresting means.

ll. in a gyroscopic instrument the combination comprising a source of direct current, a motor generator set havingV input terminais for4 connection to said sourc'erof direct current and output terminals for supplying alternating current, a gyroscope spinningmotor, a relay reversing Y switch shiftable between two positions and connecting said output terminals Yto said spinning motor for rotation in one direction, when in one of said positions, and for rotation in the opposite direction, when in the other one of said positions, a relay switch shiftable between Vtwo positions and connecting said inputterminals to said source of direct current when in one of said last mentioned positions, and amanually operable switch shiftable between two positions and controlling said relay switcb'for starting .said motor Generator set, when in one of said'positions,

and for shifting'said reversing relay switch when moved to the other one of its positions', and a timing control relay operable by said reversing relay switch and opera-V tive to controlV said relay switch for disconnecting said input terminals from said source of current, after an interval has elapsed upon the shifting of said relay reversing switch.

References Cited by the Examiner UNITED STATES PATENTS Perry et al. 33-226 Rossiter 33-226 Ansehutz-Kaempfe 33-226 Holmes S21-204.64 X Fung.

Anschutz-Kaempfe 33-226 Carlson 33-204 X FOREIGN PATENTS France. Germany. Germany. Great Britain.

ROBERT B. HULL, Primary Examiner. ISAAC LISANN, Examiner. 

1. STATIONARY GYROSCOPIC COMPASS COMPRISING A CONTAINER, A LIQUID FILLING SAID CONTAINER, A FLOAT IN SAID LIQUID, MEANS MOUNTED ON AT LEAST ONE OF THE ELEMENTS FORMED BY SAID CONTAINER AND SAID FLOAT FOR EXERTING A FORCE ON SAID FLOAT MAINTAINING THE FLOATING CONDITION THEREOF, A GYROSCOPE CARRIED BY SAID FLOAT WITH ITS AXIS OF ROTATION IN HORIZONTAL POSITION, SAID CONTAINER AND SAID FLOAT HAVING A SHAPE AFFORDING FREEDOM FOR RELATIVE ROTATION ABOUT A VERTICAL AXIS AND THE CENTER OF GRAVITY OF SAID FLOAT AND THE ELEMENTS CARRIED THEREBY INCLUDING SAID GYROSCOPE BEING LOCATED A SUBSTANTIAL DISTANCE BELOW THE CENTER OF BUOYANCY OF SAID FLOAT, A THEODOLITE MOUNTED ON SAID CONTAINER FOR ROTATION ABOUT SAID VERTICAL AXIS, SENSING MEANS CONNECTED WITH SAID THEODOLITE FOR SENSING THE ANGULAR POSITION OF SAID THEODOLITE RELATIVE TO SAID FLOAT WITH RESPECT TO SAID VERTICAL AXIS, SAID FIRST-NAMED MEANS INCLUDING A FLEXIBLE ELONGATED VERTICAL SUSPENSION MEMBER DISPOSED ABOVE SAID FLOAT AND HAVING ITS LOWER END FIXED TO SAID FLOAT AND ITS UPPER END TO SAID THEODOLITE, A FOLLOW-UP MOTOR CONNECTED WITH SAID CONTAINER AND TO SAID THEODOLITE FOR PRODUCING RELATIVE ROTATION THEREOF ABOUT SAID VERTICAL AXIS, CONTROL MEANS CONNECTED TO SAID SENSING MEANS AND TO SAID MOTOR FOR CAUSING THE LATTER TO IMPART FOLLOW-UP ROTATION TO SAID THEODOLITE RELATIVE TO SAID FLOAT KEEPING SAID SUSPENSION MEMBER IN RELAXED CONDITION, AND DAMPING MEANS ON SAID FLOAT TO DAMPEN ROTARY OSCILLATIONS THEREOF ABOUT SAID VERTICAL AXIS, THE SPIN OF SAID GYROSCOPE BEING SO CORRELATED TO THE WEIGHT OF SAID FLOAT AND OF THE ELEMENTS CARRIED THEREBY, TO SAID BUOYANCY, TO SAID DISTANCE AND TO THE DAMPING FORCE EXERTED BY SAID DAMPING MEANS AS TO RESULT IN A PERIOD OF SAID OSCILLATIONS AMOUNTING TO A FEW MINUTES AND IN A REDUCTION OF THE AMPLITUDE OF SAID OSCILLATIONS TO SUBSTANTIALLY ZERO WITHIN A PERIOD OF THE ORDER OF TEN MINUTES. 